SUMMARY The human enteric nervous system (ENS) is a complex network of ~500 million neurons derived from the enteric neural crest (ENC) and essential for gastro-intestinal (GI) function. ENS defects are the cause of many common human disorders including gastroparesis, irritable bowel syndrome (IBS), hypertrophic pyloric stenosis. Hirschsprung's disease (HD) is a severe congenital defect characterized by the lack of ENS precursors in the distal portions of the gut referred to as aganglionosis. Aganglionosis results in the lack of proper peristalsis causing functional colonic obstruction (megacolon) Development of the human ENS is poorly understood given the lack of accessible tissue. The use of human pluripotent stem cells (hPSCs) represent an novel and unique strategy to access human ENS development and to model and potentially treat HD. Very recent work from our group demonstrates the feasibility of generating ENC from human PSCs and sets the stage for using the technology for developing drug and cell based strategies in treating HD and potentially other ENS disorders. The current application builds on such exciting preliminary work to pursue three specific aims: In Aim 1, we will establish conditions to characterize and manipulate the broad repertory of neuronal subtypes and enteric glia from hPSCs and to test their function in innovative co-culture assays with known target cells. In Aim 2, we will apply ENC differentiation technology to model HD in hPSCs and to validate current and identify novel candidate HD drugs. In Aim 3, we will optimize hPSC-based cell therapy approaches in a mouse model of HD and perform mechanistic studies that define the critical parameters for in vivo rescue of HD animals. Our study is unique as it represents the first effort to reliably recreate and study early human ENS lineages in vitro. The collaborators assembled for this proposal have complementary expertise in hPSCs, ENS biology, chemical screening and cell transplantation. The ENS is a structure that is not sufficiently studied by others despite its important contribution to human health. Our study has the potential to directly yield novel drug and cell based treatments for HD. The work sets the stage and develops the technology necessary for the broader community to study ENS development and ENS function in human health and disease.